1. Field of the Invention
The present invention relates to a vehicular air conditioner having a cooling unit and a heating unit, for adjusting the temperature in a vehicle cabin with the cooling unit and the heating unit.
2. Description of the Related Art
Vehicular air conditioners installed on vehicles adjust the temperature and humidity in the passenger compartment by mixing air cooled by an evaporator serving as a cooling unit and air heated by a heater core serving as a heating unit with each other at a desired mixing ratio and thereafter delivering the mixed air from a defroster outlet, a face outlet, or a foot outlet of the passenger compartment into the passenger compartment.
In such vehicular air conditioners, the air cooled by the evaporator flows substantially straight from an air mixing door through a cooling air passage defined in a housing into a mixing chamber. Part of the air is introduced into a hot air passage and heated by the heater core. The heated air flows upwardly through the housing into the mixing chamber. The air introduced into the cooling air passage is mixed with the heated air in the mixing chamber, so that the mixed air is adjusted to a desired temperature. The mixed air is then supplied through a set of discharge switching doors selectively to a defroster air passage, a face air passage, or a foot air passage. For details, see Japanese Laid-Open Patent Publication No. 10-236134 and Japanese Laid-Open Patent Publication No. 2002-274149, for example.
In recent years, there has been employed in the art a vehicular air conditioner which is capable of supplying air that has been adjusted to a desired temperature to rear seats as well as front seats in the vehicle passenger compartment.
As shown in FIG. 13 of the accompanying drawings, such a vehicular air conditioner 1 has a rear seat face air passage 3 communicating with rear seat face openings that are open toward the rear seats. The rear seat face air passage 3 is defined adjacent to a foot air passage 2 in an air conditioner case 4. The air conditioner case 4 houses therein a foot/face switching door 7 for switching between the rear seat face air passage 3, a face opening 5, and the foot air passage 2. Air introduced from an air inlet 8 defined in the air conditioner case 4 is cooled by an evaporator 9 housed in the air conditioner case 4. Part of the air is heated by a heater core 10 housed in the air conditioner case 4. The cooled air and the heated air are mixed with each other by an air mixing portion 11, so that the mixed air is adjusted to a desired temperature. The mixed air is supplied by the foot/face switching door 7 selectively to the rear seat face air passage 3, the face opening 5, and the foot air passage 2. For details, see Japanese Laid-Open Patent Publication No. 2000-71748, for example.
The vehicular air conditioner disclosed in Japanese Laid-Open Patent Publication No. 2000-71748 adds the rear seat face air passage 3 for supplying temperature-adjusted air to rear seats, to the vehicular air conditioners disclosed in Japanese Laid-Open Patent Publication No. 10-236134 and Japanese Laid-Open Patent Publication No. 2002-274149.
Generally, the vehicular air conditioner 1 is required to mix the cooled air and the heated air into well mixed air in order to increase the comfort of passengers in the passenger compartment.
In the vehicular air conditioner 1, the air supplied from the air inlet 8 is cooled by the evaporator 9 and flows substantially straight through an air passage 12 into the air mixing portion 11, and the air supplied to the heater core 10 is heated by the heater core 10 and then flows upwardly into the air mixing portion 11. Therefore, in the air mixing portion 11 where the cooled air and the heated air are mixed with each other, the cooled air tends to flow through an upper portion of the air conditioner case 4 into the face opening 5, and the heated air tends to flow along the foot/face switching door 7 into the rear seat face air passage 3 and the foot air passage 2.
As a result, the temperature of the air discharged from the face opening 5 into the passenger compartment and the temperature of the air delivered through the rear seat face air passage 3 and discharged from the rear seat face opening into the passenger compartment are liable to differ from each other. Specifically, the temperature of the air discharged from the rear seat face opening tends to be higher than the temperature of the air discharged from the face opening 5 which opens toward the front seats. As a consequence, the temperature of the air delivered to the rear seats tends to be higher than the temperature of the air delivered to the front seats. Therefore, the passengers on the rear seats do not feel as comfortable as the passengers on the front seats.
Another problem is that since the mixed air produced in the air conditioner case 4 needs to be supplied from the air conditioner case 4 through the rear seat face air passage 3 to the rear seats, the discharged air undergoes a large resistance as it flows through an air passage extending from the air conditioner case 4 to the rear seats. The amount of air delivered from the rear seat face opening to the rear seats is thus relatively small. Therefore, the rear seats are not supplied with the same amount of air as the front seats from the vehicular air conditioner 1, and the passengers on the rear seats do not feel as comfortable as the passengers on the front seats.